Mary received a flu vaccine. Why didn't the vaccine make her sick?

Mary didn't get sick from the flu vaccine because it contains the smaller portion of the flu which isn't strong enough to infect you. Moreover, your white blood cells attack the portion of the flu while the memory cells take note of the flu, so when it comes next time, it won't affect your body because it knows how to fight the virus.

Hope this helps!

estuaries are the partially enclosed coastal bodies of brackish water formed at the mouth of sea where river meets an ocean. it is a transition zone between river and sea water so estuaries are influenced to both marine environment such as tides, waves and to riverine such as flow of fresh water and sediments. the mixing of sea and fresh water provide high level of nutrients, making estuaries a high product habitats.

many estuaries suffers degradation from a variety of human activities like erosion from deforestation, overgrazing, overfishing, drainage and eutrophication.

so from the above statement answers will be

1. false as estuaries are formed due to both brackish and freshwater.

2.true, due to high productivity estuaries are breeding ground for many marine species.

3. direct and indirect activities of man that contribute to pollution and deposition of sediments.